1. Field of the Invention
The present invention relates to a controller for diesel electric locomotive which converts output from a diesel engine into electric power and supplies alternating current power to a driving induction motor.
2. Description of the Related Art
FIG. 6 is a block diagram which shows a configuration of a related controller for diesel electric locomotive. In FIG. 6, an alternating current generator 2 which is directly connected to a diesel engine 1 generates alternating current power. The alternating current power is rectified into direct current power by a rectifier 3. The direct current power is further inverted into alternating current by a VVVF inverter 4 for power control of an induction motor 5 so as to carry out speed control of the diesel electric locomotive at the time of power run.
Additionally, if input voltage at the VVVF inverter 4 exceeds a set value due to wheel slip that occurs at the time of power run, voltage detecting means 6 detects over-voltage to carry out predetermined protective action.
When a brake is applied, in addition to idling operation of the diesel engine 1, the voltage detecting means 6 detects the voltage generated by the induction motor 5 and the brake chipper 8 is controlled for a conduction ratio by a conduction ratio control means 7 in accordance with the generated voltage. The energy generated by the induction motor 5 is consumed at a brake resistor and thus speed of the diesel electric locomotive is reduced.
With the structure of the related controller for diesel electric locomotive, if a re-cohesion control for reducing output torque of the induction motor 5 fast is carried out when wheel slip has occurred due to road surface conditions at the time of power run, failure in following-up decrease in the diesel engine output causes an abnormal increase in revolving speed of the diesel engine. This results with overvoltage at the input voltage of the VVVF inverter 4 due to an increase in output voltage of the alternating generator 2 and thus causes a problem that the voltage detection means 6 carries out the protective actions.